High-lift systems are designed to allow a transport aircraft—with typical transonic cruise speeds—to safely operate at low speeds for landing and takeoff operations. High-lift devices allow the use of a more efficient wing in flight, while adding more lift for takeoff and landing operations. These devices tend to re-shape the wing section to give it more camber, and therefore more lift. Current high-lift systems for low-speed flight conditions are complex systems in which cruise efficiency and acoustic performance are sacrificed during takeoff and landing operations.
Current high-lift systems are usually slotted both on the leading edge and the trailing edge of the wing to take advantage of the aerodynamic properties of slotted flows and to achieve the necessary high lift performance. The slotted leading and trailing edge devices, and the associated sub-systems necessary to change the wing configuration from cruise to low-speed conditions, are complex and employ a significant number of parts to enable safe operation. In addition, these complex mechanical high-lift systems (e.g., Fowler flap mechanisms) often protrude externally under the wings, and thus often require external fairings, that result in increased cruise drag.
In contrast to the complex mechanical high lift systems currently in use (e.g., Fowler flap mechanisms), simple hinged flaps are the simplest and most basic flaps for high-lift design. However, simple hinged flaps are currently not used in high-lift systems of transport aircraft because simple hinged flaps are vulnerable to flow separation at high flap deflections for both trailing edge and leading edge applications. Therefore, what is needed for transport aircraft, is a flow control method that enables a simple hinged flap system to achieve higher flap deflections without flow separation, and thereby achieve lift enhancement comparable to a complex conventional systems (e.g., Fowler-flap systems).